In modern wireless communications systems, the target to make more cost efficient and less power consuming devices has led to a need to increase integration level. The integration level can be increased, for instance, by using a conversion device which combines both a digital-to-analog converter and a mixer. This kind of a conversion device can offer digital-to-analog conversion in association with radio frequency generation.
In the direct digital-to-radio frequency (RF) conversion described above, interfering image components are generated into a spectrum due to sampling carried out in digital-to-analog (D/A) conversion. In the prior art, these image components are attenuated by a filter placed after the D/A conversion. The filters, however, make the structure of a converter more complicated.